The use of semipermeable membranes for effecting liquid separations has become well accepted, and membranes both for ultrafiltration applications and reverse-osmosis applications are presently in use for a wide spectrum of applications, including water purification, concentration of dilute mixtures or solutions, and waste treatment and/or recovery of recyclable components. A large variety of semipermeable membranes have been developed, and spiral-wound cartridges have been one accepted type of device which has been found valuable for efficiently providing a large amount of membrane surface area within a given spatial volume. While such spiral cartridges utilizing sheetlike membranes have proved satisfactory and have given good performance in many applications, improvements in devices of this type are constantly being sought, as no single separation device has yet proven to provide the best performance in every type of situation, particularly when considering the wide variations in feed materials that are encountered. Especially troublesome are liquid feed materials that carry particulate contaminants that tend to frequently plug sheet-like semipermeable membranes and liquid feed mixtures which are high in viscosity.
Accordingly, improvements in the design of such spiral wound membrane cartridges continue to be sought after.